Flameproofing combustible sheet materials

ABSTRACT

A flameproofing agent is applied to combustible sheet material in a pattern in which small areas of high concentration of flameproofing agent are distributed substantially uniformly on the sheet material and alternate with areas of low to zero concentration of the flameproofing agent.

United States Patent Lauchenauer Oct. 23, 1973 [54] FLAMEPROOFINGCOMBUSTIBLE SHEET 3,700,760 10/1972 Benghiat 117/136 MATERIALS 3,671,2846/1972 Uhrig 117/37 R 3,671,303 6/1972 Meitner 117/136 [75] Inventor:Alfred E. Lauchenauer, Thurgau, 3,101,520 8/1963 George eta]. 117 37 RSwitzerland 3,490,985 1/1970 Marzocchi et a1. 117/37 R 3,360,392 12/1967Mod et a1 117/37 R [73] Asslgleei Radune and 3,663,463 5 1972 Wren117/136 Switzerland [22] Filed: Feb, 7, 1972 Primary Examiner-William D.Martln 1 1 pp N05 224,346 Assistant Examiner-Dennis Cv KonopackiAttorney-Dexter N. Shaw et a1.

[30] Foreign Application Priority Data Feb. 12, 1971 Great Britain4,552/71 [57] ABSTRACT [52] [1.8. CI 117/37 R, 117/136, 117/137,

, A flameproofing agent is applied to combustible sheet [5 Int. materialin a pattern in small areas of con. 8.] Field 1 Search l17/37 137,centration of flameproofing agent are distributed subl17/133 stantiallyuniformly on the sheet material and alternate with areas of low to zeroconcentration of the [56] References Cited flameproofing agent.

UNITED STATES PATENTS 3,691,275 9/1972 Benghiat 117/136 16 Claims, N0Drawings l FLAMEPROOFING COMBUSTIBLE SHEET MATERIALS The presentinvention relates to the flameproofing of sheet materials.

Hitherto the flameproofing treatments of sheet material, in particulartextile sheet material such as fabrics has been carried out by paddingonto such sheet material solutions or dispersions of suitableflameproofing agents, i.e., by impregnating the sheet material withaqueous or non-aqueous solutions or dispersions of such agents followedby squeezing between the rollers of a mangle to remove the excess ofthebath. Since rather high amounts of flameproofing agents are necessaryto achieve a substantial reduction of the rate of burning or of flamepropagation, such flameproofing or flame-retarding treatments tendtoaffectthe handle of treated textile sheet material seriously, i.e., theycause stiffening due to the reduction of fiber to fiber and yarn to yarnmobility. In the case of synthetic thermoplastic material, which has amuch lower bath take-up than cellulosic or wool fibers, it is in mostcases impossible to apply by padding amounts of flame-retarding agentssufficient to produce improvements in the flameretardance, and one hadto resort to coating, which affects the properties of'thesheet'material, and in particular the handle to such an extent that suchcoated fabrics could no longer be used for apparel fabrics and othertextile applications.

All these flameproofing or flame-retarding treatments produced acontinuous coatingor an enclosure of all individual fibers ofthe entiresheetmaterial, and it was believedthatit was important'to have the agentdistributed as uniformly as possible over the surface of fibers, yarnsand fabrics.

According to the present invention an improved and more universallyobtainable flame-retardant effect can be achieved if agents having aflame-retarding action are present on sheet material, in particulartextile sheet material, in the form of a pattern only locally, i.e.,where areas with a high concentration of the agent alternate with areaswith low tozero concentration of such agents, and where the averagedistance between areas of high concentration of flame-retarding agentspreferably is at most ten times, preferably less than five times thethickness of the sheet material.

The present invention also includes a process for impartingflame-retardant properties to sheet material by applying agents whichhave a flame-retarding action to said sheet material in the form of apattern, in which areas with a high concentration of the agent alternatewith areas' with low to zero concentration of such an agent.

This local application of flame-retardingagents has been found toproduce at the same total concentration of the agent on the weight ofthe sheet material, flameretarding effects of at least the samemagnitude as with a uniform distribution (all-over distribution) offlameretarding agents even though there is no or relatively littleflame-retarding agent present between the areas of high concentration.The handle, stiffness or drape of sheet material containingflame-retarding agents only locally is much less affected than by auniform application in the same concentration of the same flameproofingagent. By the term flame-retarding agent" is to be understood any agentwhich, when applied to a certain sheet material, is capable of reducingthe rate at which a flame propagates itself along this sheet material,or

which reduces the ease of ignition of this sheet material, i.e., whichforinstance increases the time during which the sheet material has to beexposed to a defined source of heat such as a flame until it ignites, orwhich increases the amount of heat required to ignite the sheetmaterial, or which enhances the ease of extinction of the flame on theburning sheet material.

Many different methods have been proposed for the evaluation offlame-retarding or flameproofing effects,

either by determining the rate of propagation of a flame through asample of sheet material, which may be at any angle between 0 to 9 tothe horizontal plane, by measuring the oxygen consumption rate of aflame on the material to be tested, the rate or ease of ignition,ignition temperatures, ease of extinction, length of the charred areaand so on. Such methods are for instance described in Textile Chemistand Colorist 2 (1970), p. 123125.-Such flame-retarding agents may acteither by giving off gases which do notsupport combustion and thusdisplace oxygen in the air present in and around the sheet materialexposed to a flame, by forming a virtually non-combustible coatingaround the components of the sheet material if exposed to ignitiontemperatures, by catalytic or chemical interaction with the material ofthe sheet material or components thereof, or with gases developingduring burning, by influencing thermal decomposition characteristics(such as for instance by lowering the thermal decomposition temperatureof the material to below its ignition temperature), the ignitiontemperature or the heat of combustion or the heat capacity of the sheetmaterial or componentsthereof. The mechanism of the action'offlame-retarding agents is still not completely understood. Such agentsare believed to act by decomposing at temperatures equal to or below thetemperature of the flame and-or to have a catalytic effect at thesetemperatures on gases given off during burning, on the burning materialitself, or both. In some cases they may act by dissipating heat or bydecomposing into noncombustible gases.

Different types of flame-retarding agents are known which all may beused for products and processes according to the present invention perse or in mixtures. Agents giving off non-combustible gases comprisehalogen compounds having a relatively low decomposition temperature, inparticularly organic chloro and bromo compounds, compounds containingboron, nitrogen compounds, in particular ammonium salts of acids andnitrogen compounds where nitrogen is bonded to other atoms withpreferably only one bond. Most widely used among flame-retarding agentswhose active ingredient remains predominantly in the charred product,are inorganic and in particular organic phosphorous compounds, which atleast in the case of cellulose are believed to change catalyticallythemechanism' of thermal decomposition. Other elements present as activeingredients in flame-retarding agents are molyb-' denum, antimony,silicon, aluminum and other polyva-' rics, but also in sheets of foam,plastics, and wood. They are present in the form of an irregular orrandom or a regular pattern, where the areas of high concentrations ofthose agents may or may not be interconnected, i.e., where the agent maybe present for instance in the form of dots (not interconnected) orlines alone or dots interconnected by lines, or in any other patternwhere between areas of high concentration on the agent there are areaswith relatively low or zero concentration of the flame-retarding agent.The total amount of flame-retarding agents applied to the sheet materialis between 2 and 30 percent, usually between 5 and 15 percent of theweight of the sheet material depending on the agents used andflame-retarding requirements. The areas of high concentration may liewithin the body of the sheet material, i.e., imbedded in the sheetmaterial without adding to its thickness (this is particularly useful ifthe sheet material is relatively thick) or they may only partlypenetrate in the sheet material or sit virtually only on its surface(thus increasing the thickness of the sheet material) on either or bothsides or faces of the sheet material.

Generally speaking the total area of the areas of low or zeroconcentration of the flame-retarding agent should not exceed the totalarea of the area of high concentration by a factor of more than 10,preferably 5. The distance between the edges of high concentration areasshould not be more than five times, preferably three times or less thanthe median diameter of the high concentration area, and the distancebetween high concentration areas should be less than times, preferablyfive tiems or less the thickness of the sheet material. In the case ofthin sheet material (for instance up to the thickness of a poplin fabricor of print cloth) the flameretarding material may sit on the surface ofthe sheet material on either or both sides depending on the pattern andthe flame-retardancy requirements, without substantially penetratinginto the sheet material.

This minimizes stiffness due to blocking of interfiber movement. In thecase of thicker sheet material it is advantageous to have moreflame-retarding material present within the structure of the sheetmaterial, particularly if a high degree of flame-retardancy is required.More blocking of interfiber mobility will, however, take place whichwill result in increased stiffness, which stiffness of course will stillbe lower than if the flameretarding agent would be distributed evenlythroughout the sheet material.

Flame-retarding agents may be present in pure form or together withthermoplastic or non-thermoplastic binders, finishing agents, white orcolored pigments, etc. They may be applied in the form of dispersions,emulsions, dry powders or pastes by known methods such as printing, drypowder application (scattering, powder-dot transfer), and spraying.These agents may at the time they are applied already be polymeric orthey may be subsequently transformed into polymers, be chemicallymodified or reacted with other agents present or with the sheet materialor components thereof.

The sheet material may consist of cellulose or derivatives thereof, ofproteinic material such as present in wool, of synthetic thermoplasticpolymers such as polymerisates, co-polymerisates or mixed polymerisatesof acrylic, vinylic, olefinic monomers, of lactams or lactones, or theymay be polycondensates of polyhydroxy-compounds and poly-hydroxylicacids, of

poly-carboxylic acids and polyamines, of poly-hydroxy compounds andisocyanates or mixtures of such polymers. These polymers may be presentas fibers in the form of textile fabrics (woven, knitted or non-woven),as films, sheets containing or consisting of one or more polymericcomponents, as paper, cardboard or woodlike sheet material, sheets offoam or laminates of two or more of the sheet materials mentioned. Suchsheet material, if present in the form of textile fabrics, may be giventhe flame-retarding treatment according to the present invention at anystage of finishing, but preferably this treatment is applied as one ofthe last steps in the finishing sequence. Such sheet material, whetherpresent in the form of textile fabrics or otherwise, may be coated withpolymeric material and/or be mechanically deformed for instance byembossing or pressing prior or subsequent to being given theflame-retarding treatment according to the present invention. By theterm sheet material is to be understood a shape that is thin in relationto its length and breadth. It may be sheetlike in the sense of sheets offabrics of paper or of films, where a thin material is present inlengths exceeding the width by a factor of 10, 20 or more or it mayconsist of parts cut from such sheets or formed in that way. It has beenfound possible to apply flameretarding agents according to the presentinvention in a discontinuous form on only one side of the face of thesheet material or on both. A one-sided localized application isparticularly useful in cases where fabrics in actual use are exposed tothe accidental action of an incendiary only from one side and where theflameretarding agent thus can be located on the invisible side of thematerial where it cannot unfavorably affect other properties as wouldthe same agent if distributed evenly throughout the sheet material.

The discontinuous, pattern-like application of flameretarding agentsalso has the advantage that one may apply agents in the form ofpigments, powders, in molten form, in the form of soluble or insolublepolymers, dispersions, emulsions, etc., i.e., one has a much widerchoice of formulation and thus may use agents which could not be used byconventional methods leading to a uniform distribution throughout thesheet material or by coating. Even though there are areas where thereare high concentrations of the flame-retarding agent than if the sameagent is distributed uniformly throughout the sheet material, therealways will be areas in between the high concentration areas which arenot affected at all by the presence of the flame-retarding agent andthus will bend very easily. Total stiffness thus is much lower than ifthe same amount of the same agent is uniformly distributed over thesheet material.

Following is a description by way of example only of methods of carryingthe invention into effect.

Example I A cotton broad cloth which had been desized, bleached,mercerized and given a wash and wear finish was treated with a pastecontaining 2.4 g. Carbopol as a thickening agent and 20 g. diammoniumphosphate as the flame-retarding agent in ml of water was printed on oneside in a pattern of dots, each dot having a diameter of 0.8 mm. and thedots being disposed in rows so that the distance between the edges ofadjacent dots is 1 mm. and the total high concentration area is 20percent of total cloth area. The amount of flameretarding agent appliedto the fabric was 5 percent of the weight of the fabric.

Example II (Comparison) The fabric of Example I was padded in an aqueoussolution of diammonium phosphate as a flameretarding agent, the add-onbeing adjusted in such a way that the fabric also contained 5 percentdiammonium phosphate, uniformly distributed thereon. The treated sampleof Example I in which the flameretarding agent was present in adiscontinuous form had a softer handle than the sample of Example II inwhich the agent was distributed uniformly throughout the fabric. The twosamples and an untreated control were tested according to AATCC 33-1962(45 configuration of the fabric).

Sample 1 (dots): Burning time 6.4 sec. Sample 2 (uniform distribution):Burning time 6.5 sec. Control (untreated): Burning time 4.0 sec.

Example III Examples I and II were repeated, the add-on of diammoniumphosphate this time being percent on the weight of the fabric. Whensubjected to the same burning test neither fabric sample burned.

Example IV The sample treated according to Example I was wrapped arounda piece of polyurethane foam. The same was done with an untreatedcontrol. A gas flame (length 2 cm) was directed towards the two samplesfor 7 seconds. The foam wrapped in the control started to burnimmediately, while the flame on the foam wrapped in fabric treatedaccording to Example I died after the gas flame had been removed, bothwhen the dots were on the inside or on the outside of the wrappingfabric.

Example V Example I was repeated for a 50:50 cotton/polyester blend(shirting), the treatment being applied to one side only, and the amountof flame-retardant being present on the fabric in an amount of 5 percentby weight on the weight of the fabric. On conducting burning tests at 45configuration of fabric and on contact with a gas flame for one second aslight melting of the polyester was noted and the flame died after asecond. An identical test on an untreated control resulted in meltingand burning of the polyester.

Example VI Example V was repeated for a polyester blouse material. Inthe burning tests, the treated material melted slightly and the flamedied immediately on removal from the gas flame. The untreated melted'andburned.

Example VII A cotton poplin (desized, bleached, mercerized and vat dyed,weight 120 g/m") was padded in an aqueous solution containing 400 gwater and 600 g Flammentin AC (a 50 percent solution of an organiccompound containing halogen, phosphor and nitrogen atoms, made by Quehl,Speyer, Germany). The solids add-0n after squeezing and drying was 25percent on the weight of the fabric (sample A, treated control).

A second sample was prepared in the same way, but with an add-on of only20 percent solids (sample B, treated control B).

On two samples (samples C and D) of the same poplin, the sameflameproofing agent (Flammentin AC) was screen-printed in the form of athickened paste (522,5 g Flammentin AC, 50 percent solids; 322,5 gMeyprogum AC 7 as thickening agent. Meyprogum is galactomannane, sold byMeyhall Chemical AG, Kreuzlingen, Switzerland).

add-on of flame Test Result proofing agent Sample (A) (treated control):uniform distribution of flame proofing agent does not ignite (B)(treated control): 20% ignites, stops uniform distribution burning after5 seconds (B):discontinuous l3% ignites, flame distribution stopsburning after 5 seconds (C):discontinuous 19% does not ignitedistribution Untreated control ignites, completelyburnt after 12 secondsExample VIII A cotton/polyester blend (50/50) after desizing andbleaching was padded in a solution of 200 grams/liter of diammoniumphosphate, then squeezed and dried. The add-on of solids was 12 percenton the weight of the fabric (sample A, treated control).

To the same fabric (sample B) the same amount of the same flameproofingagent was applied by printing by means of the screen printing methoddescribed in Example 7, 34 percent of the screen being open. Theflameproofing agent thus was present on the sample in the form of dotsseparated by areas of fabric not con- 1 taining any flameproofing agent.The area covered by dots was about one third of the total area.

Flammability tests were carried out as described in Example 7.

Flammability Sample Add-on (A) uniform distribution 12% ignites, stopsburnof flame proofing agent ing after 4 seconds (B) local application ofl2% does not ignite What is claimed is:

1. A process for flameproofing combustible sheet material whichcomprises applying to said sheet material a pattern of a flameproofingagent in which small areas of high concentration of flameproofing agentare distributed substantially uniformly on said sheet material andalternate with areas of low to zero concentration of flameproofingagent, said areas of low to zero concentration not exceeding said areasof high concentration by a factor of about 10, and the distance be-,

tween said areas of high concentration being less than about 10 timesthe thickness of said sheet material, the

flame-proofing agent is less than about five times the thickness of saidsheet material.

4. The process according to claim 1 wherein the total area of the areasof low to zero concentration of flameproofing agent does not exceed thetotal area of the small areas of high concentration of flameproofingagent by a factor of more than about 5.

5. The process according to claim 1 in which the distance between theedges of adjacent small areas of high concentration of flameproofingagent is not more than about five times the mean diameter of said areasof high concentration.

6. The process according to claim 1 in which the distance between theedges of adjacent small areas of high concentration of flameproofingagent is not more than about three times the mean diameter of said areasof high concentration..

7. The process according to claim 1 wherein said sheet materialcomprises textile sheet material.

8. The process according to claim 1 wherein said small areas of highconcentration of flameproofing agent comprise a regular pattern ofdisconnected dots on the surface of said sheet material.

9. A flameproof sheet material comprising an ordinarily combustiblesheet material having a flameproofing agent applied thereto in a patternin which small areas of high concentration of the flameproofing agentare distributed substantially uniformly on said sheet material andalternate with areas of low to zero concentration of flameproofingagent, said areas of low to zero concentration not exceeding said areasof high concentration by a factor of about 10, and the distance betweensaid areas of high concentration being less than about 10 times thethickness of said sheet material, the total amount of flameproofingagent applied to said sheet material being from about 2 to about 30percent, by weight, based on the weight of said sheet material.

10. A flameproof sheet material according to claim 9 wherein the totalamount of flameproofing agent applied to said sheet material is fromabout 5 to about 15 percent, by weight, based on the weight of saidsheet material.

11. A flameproof sheet material according to claim 9 wherein thedistance between said small areas of high concentration of flameproofingagent is less than about five times the thickness of said sheetmaterial.

12. A flameproof sheet material according to claim 9 wherein the totalarea of the areas of low to zero concentration of flameproofing agentdoes not exceed the total area of the small areas of high concentrationof flameproofing agent by a factor of more than about 5.

13. A flameproof sheet material according to claim 9 wherein thedistance between the edges of adjacent small areas of high concentrationof flameproofing agent is not more than about five times the meandiameter of said areas of high concentration.

14. A flameproof sheet material according to claim 9 wherein thedistance between the edges of adjacent small areas of high concentrationof flameproofing agent is not more than about three times the meandiameter of said areas of high concentration.

15. A flameproof sheet material according to claim 9 wherein said sheetmaterial comprises textile sheet material.

16. A flameproof sheet material according to claim 9 wherein said smallareas of high concentration of flameproofing agent comprise a regularpattern of disconnected dots on the surface of said sheet material.

2. The process according to claim 1 wherein the total amount offlameproofing agent applied to said sheet material is from about 5 toabout 15 percent, by weight, based on the weight of said sheet material.3. The process according to claim 1 wherein the distance between saidsmall areas of high concentration of flame-proofing agent is less thanabout five times the thickness of said sheet material.
 4. The processaccording to claim 1 wherein the total area of the areas of low to zeroconcentration of flameproofing agent does not exceed the total area ofthe small areas of high concentration of flameproofing agent by a factorof more than about
 5. 5. The process according to claim 1 in which thedistance between the edges of adjacent small areas of high concentrationof flameproofing agent is not more than about five times the meandiameter of said areas of high concentration.
 6. The process accordingto claim 1 in which the distance between the edges of adjacent smallareas of high concentration of flameproofing agent is not more thanabout three times the mean diameter of said areas of high concentration.7. The process according to claim 1 wherein said sheet materialcomprises textile sheet material.
 8. The process according to claim 1wherein said small areas of high concentration of flameproofing agentcomprise a regular pattern of disconnected dots on the surface of saidsheet material.
 9. A flameproof sheet material comprising an ordinarilycombustible sheet material having a flameproofing agent applied theretoin a pattern in which small areas of high concentration of theflameproofing agent are distributed substantially uniformly on saidsheet material and alternate with areas of low to zero concentration offlameproofing agent, said areas of low to zero concentration notexceeding said areas of high concentration by a factor of about 10, andthe distance between said areas of high concentration being less thanabout 10 times the thickness of said sheet material, the total amount offlameproofing agent applied to said sheet material being from about 2 toabout 30 percent, by weight, based on the weight of said sheet material.10. A flameproof sheet material according to claim 9 wherein the totalamount of flameproofing agent applied to said sheet material is fromabout 5 to about 15 percent, by weight, based on the weight of sAidsheet material.
 11. A flameproof sheet material according to claim 9wherein the distance between said small areas of high concentration offlameproofing agent is less than about five times the thickness of saidsheet material.
 12. A flameproof sheet material according to claim 9wherein the total area of the areas of low to zero concentration offlameproofing agent does not exceed the total area of the small areas ofhigh concentration of flameproofing agent by a factor of more than about5.
 13. A flameproof sheet material according to claim 9 wherein thedistance between the edges of adjacent small areas of high concentrationof flameproofing agent is not more than about five times the meandiameter of said areas of high concentration.
 14. A flameproof sheetmaterial according to claim 9 wherein the distance between the edges ofadjacent small areas of high concentration of flameproofing agent is notmore than about three times the mean diameter of said areas of highconcentration.
 15. A flameproof sheet material according to claim 9wherein said sheet material comprises textile sheet material.
 16. Aflameproof sheet material according to claim 9 wherein said small areasof high concentration of flameproofing agent comprise a regular patternof disconnected dots on the surface of said sheet material.